#!/usr/bin/perl
use strict;
use warnings;

my @str = 
    map {$_->[0]}
    sort {$a->[1] <=> $b->[1]} 
    map {chomp; [$_, length($_)]} <DATA>;
print LCS(@str), "\n";

sub LCS {
    my @str = @_;
    my $next = combo(split //, $str[0]);
    SUBSEQ:
    while (my @subseq = $next->()) {
        my $regex = join '.*', @subseq;
        $regex = qr/$regex/;
        for (1 .. $#str) {
            next SUBSEQ if $str[$_] !~ /$regex/;
        }
        return join '', @subseq;
    }    
}
sub combo {
    # modified [id://394168] to generate long to short
    # - my ($by, $next) = (0, 1);
    # + my ($by, $next) = ($#list + 2, 1);
    # - $by++;
    # - return () if $by > @list;
    # + $by--;
    # +return () if ! $by;
}
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